Jan
3
The year 2005 saw many new and helpful features offered to webmasters by Google, including Google Sitemaps. That’s all great and very helpful, but somehow I don’t think it’s all totally motivated by the fact that it gives them whiter, brighter teeth and a prettier smile. 
There are a lot of interesting phenomenon happening, and the beginning of 2006 called for adding a new page with a few white papers on site navigation that seem interesting, particularly those explaining the concept of “logical domains vs. physical domains.” Added here, with more to come:
Sitemaps, Domains and Website Navigation Structure
It’s no secret that Google has been working on resolving canonical issues, and that sites that do a total redesign and restructure run into problems that resemble what’s commonly referred to as “the sandbox” - which really isn’t the case, IMHO. There’s also been some speculation that not all TLDs are affected by the “sandbox” that seem to come from some sources with verifiable personal experience.
Maybe there’s a bit of information in those papers, and others yet to be added, that may shed some light on some of the factors that contribute to the drop when there’s a major change in site structure, or factors that affect different domains.
Incidentally, there was a post done on this very topic July 23, 2004 at Search Engine Watch Forums
Logical vs. Physical Domains in Site Architecture and Ranking
It was pretty much overlooked, but I think it’s an even more interesting topic now than when it was first posted.